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https://github.com/RGBCube/serenity
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DynamicLoader: Remove math functionality in favor of -lgcc
This links the dynamic linker against libgcc.a instead of having our own copy of the math functions. For now we need to specify -fbuilding-libgcc as a hack to work around a bug with the -nodefaultlibs flag. Once everyone is on the latest toolchain version this can be removed.
This commit is contained in:
Gunnar Beutner
Andreas Kling
parent
224755e6ef
commit
dd39bb7784
4 changed files with 9 additions and 198 deletions
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@ -1,6 +1,5 @@
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set(LOADER_SOURCES
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main.cpp
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math.cpp
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misc.cpp
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)
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@ -23,11 +22,13 @@ add_definitions(-D_DYNAMIC_LOADER)
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set(SOURCES ${LOADER_SOURCES} ${AK_SOURCES} ${ELF_SOURCES} ${LIBC_SOURCES1} ${LIBC_SOURCES2} ${LIBC_SOURCES3} ${LIBSYSTEM_SOURCES})
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set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-rtti -nostdlib -pie -fpic -DNO_TLS")
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# FIXME: Remove -fbuilding-libgcc after the next toolchain update
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set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fbuilding-libgcc -fno-rtti -nostdlib -pie -fpic -DNO_TLS")
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set_source_files_properties (../Libraries/LibC/ssp.cpp PROPERTIES COMPILE_FLAGS
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"-fno-stack-protector")
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add_executable(Loader.so ${SOURCES})
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target_link_libraries(Loader.so gcc)
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target_link_options(Loader.so PRIVATE LINKER:--no-dynamic-linker)
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install(TARGETS Loader.so RUNTIME DESTINATION usr/lib/)
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@ -116,4 +116,10 @@ void _start(int argc, char** argv, char** envp)
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ELF::DynamicLinker::linker_main(move(main_program_name), main_program_fd, is_secure, argc, argv, envp);
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VERIFY_NOT_REACHED();
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}
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void _fini();
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void _fini()
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{
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}
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}
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@ -1,170 +0,0 @@
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/*
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* Copyright (c) 2020, the SerenityOS developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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// TODO: Is there a compiler flag we can use to still get these math functions? (and compile with -nostdlib)
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// FIXME: What do we do with this regarding copyright stuff?
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// code for math functions taken from here:
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// https://gitlab.incom.co/CM-Shield/u-boot/commit/aa7839b39c2ee77f9ab8c393c56b8d812507dbb7
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// https://github.com/zayac/qemu-arm/blob/master/qemu/roms/ipxe/src/libgcc/__udivmoddi4.c
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// https://code.woboq.org/llvm/compiler-rt/lib/builtins/divdi3.c.html
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#include "math.h"
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extern "C" {
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union overlay64 {
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u64 longw;
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struct {
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u32 lower;
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u32 higher;
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} words;
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};
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u64 __ashldi3(u64 num, unsigned int shift)
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{
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union overlay64 output;
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output.longw = num;
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if (shift >= 32) {
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output.words.higher = output.words.lower << (shift - 32);
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output.words.lower = 0;
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} else {
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if (!shift)
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return num;
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output.words.higher = (output.words.higher << shift) | (output.words.lower >> (32 - shift));
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output.words.lower = output.words.lower << shift;
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}
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return output.longw;
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}
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u64 __lshrdi3(u64 num, unsigned int shift)
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{
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union overlay64 output;
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output.longw = num;
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if (shift >= 32) {
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output.words.lower = output.words.higher >> (shift - 32);
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output.words.higher = 0;
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} else {
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if (!shift)
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return num;
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output.words.lower = output.words.lower >> shift | (output.words.higher << (32 - shift));
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output.words.higher = output.words.higher >> shift;
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}
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return output.longw;
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}
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#define MAX_32BIT_UINT ((((u64)1) << 32) - 1)
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static u64 _64bit_divide(u64 dividend, u64 divider, u64* rem_p)
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{
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u64 result = 0;
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/*
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* If divider is zero - let the rest of the system care about the
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* exception.
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*/
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if (!divider)
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return 1 / (u32)divider;
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/* As an optimization, let's not use 64 bit division unless we must. */
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if (dividend <= MAX_32BIT_UINT) {
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if (divider > MAX_32BIT_UINT) {
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result = 0;
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if (rem_p)
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*rem_p = divider;
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} else {
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result = (u32)dividend / (u32)divider;
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if (rem_p)
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*rem_p = (u32)dividend % (u32)divider;
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}
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return result;
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}
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while (divider <= dividend) {
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u64 locald = divider;
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u64 limit = __lshrdi3(dividend, 1);
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int shifts = 0;
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while (locald <= limit) {
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shifts++;
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locald = locald + locald;
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}
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result |= __ashldi3(1, shifts);
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dividend -= locald;
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}
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if (rem_p)
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*rem_p = dividend;
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return result;
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}
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u64 __udivdi3(u64 num, u64 den)
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{
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return _64bit_divide(num, den, nullptr);
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}
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u64 __umoddi3(u64 num, u64 den)
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{
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u64 v = 0;
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_64bit_divide(num, den, &v);
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return v;
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}
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uint64_t __udivmoddi4(uint64_t num, uint64_t den, uint64_t* rem_p)
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{
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uint64_t quot = 0, qbit = 1;
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if (den == 0) {
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return 1 / ((unsigned)den); /* Intentional divide by zero, without
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triggering a compiler warning which
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would abort the build */
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}
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/* Left-justify denominator and count shift */
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while ((int64_t)den >= 0) {
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den <<= 1;
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qbit <<= 1;
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}
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while (qbit) {
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if (den <= num) {
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num -= den;
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quot += qbit;
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}
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den >>= 1;
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qbit >>= 1;
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}
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if (rem_p)
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*rem_p = num;
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return quot;
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}
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int64_t __divdi3(int64_t a, int64_t b)
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{
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const int bits_in_dword_m1 = (int)(sizeof(int64_t) * 8) - 1;
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int64_t s_a = a >> bits_in_dword_m1; // s_a = a < 0 ? -1 : 0
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int64_t s_b = b >> bits_in_dword_m1; // s_b = b < 0 ? -1 : 0
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a = (a ^ s_a) - s_a; // negate if s_a == -1
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b = (b ^ s_b) - s_b; // negate if s_b == -1
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s_a ^= s_b; // sign of quotient
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return (__udivmoddi4(a, b, (uint64_t*)0) ^ s_a) - s_a; // negate if s_a == -1
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}
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int64_t __moddi3(int64_t a, int64_t b)
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{
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const int bits_in_dword_m1 = (int)(sizeof(int64_t) * 8) - 1;
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int64_t s = b >> bits_in_dword_m1; // s = b < 0 ? -1 : 0
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b = (b ^ s) - s; // negate if s == -1
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s = a >> bits_in_dword_m1; // s = a < 0 ? -1 : 0
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a = (a ^ s) - s; // negate if s == -1
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uint64_t r = 0;
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__udivmoddi4(a, b, &r);
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return ((int64_t)r ^ s) - s; // negate if s == -1
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}
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}
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@ -1,26 +0,0 @@
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/*
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* Copyright (c) 2020, the SerenityOS developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Types.h>
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extern "C" {
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u64 __ashldi3(u64 num, unsigned int shift);
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u64 __lshrdi3(u64 num, unsigned int shift);
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u64 __udivdi3(u64 num, u64 den);
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u64 __umoddi3(u64 num, u64 den);
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uint64_t __udivmoddi4(uint64_t num, uint64_t den, uint64_t* rem_p);
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int64_t __divdi3(int64_t a, int64_t b);
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int64_t __moddi3(int64_t a, int64_t b);
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}
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